Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$204.38	13.248%	$231.4563	$231.46	$231.45	$231.50
Purchase #2	$209.60	11.298%	$233.2806	$233.28	$233.30	$233.30
Purchase #3	$49.71	9.749%	$54.5562	$54.56	$54.55	$54.60
Purchase #4	$52.46	12.780%	$59.1644	$59.16	$59.15	$59.20
Purchase #5	$206.38	5.712%	$218.1684	$218.17	$218.15	$218.20
Purchase #6	$229.71	4.355%	$239.7139	$239.71	$239.70	$239.70
Purchase #7	$239.28	7.833%	$258.0228	$258.02	$258.00	$258.00
7 purchase totals =	$1,191.52		$1,294.3626	$1,294.36	$1,294.30	$1,294.50